1. The effect of spin-orbital coupling and buffer layer to magnetic effect on Organic Light-Emitting Device
Z. Y. Sun, B. F. Ding, X. M. Ding, X. Y. Hou
Sample preparation
photon
HTL
ETL
LUMO
HOMO
Metal Cathode e- h+
Recombination
E transport layer
H transport layer
ITO Anode
Glass Substrate
The work principle of electrolumine-scence(EL) of OLED
When magnetic field (MF) is applied, the EL and the current efficiency are both enhanced comparing to the case with no MF. And as applied magnetic field increases, the magnetic effect is more obvious and becomes saturated when MF exceeds 50mT.
Experimental measurement of the magnetic effect of OLED
Because there is a competitive relationship between internal Zeeman splitting and external Zeeman splitting, therefore the existence of heavy metal element such as Au can reduce the effect of MF on OLED. And we also find that the decay of the current efficiency can make the magnetic effect more obvious.
这是超净间实验室中生长样品的有机分子束沉积系统，右边是正处于发光状态的器件。
The energy splitting induced by the applied magnetic field may the origin of the magnetic effect which can make T to S transfer easier.
Structure
1. ITO/NPB(40nm)/Alq(80nm)/LiF( 0 nm)/Ni(5nm)/Al
2. ITO/NPB(40nm)/Alq(80nm)/LiF(0.4nm)/Ni(5nm)/Al
3. ITO/NPB(40nm)/Alq(80nm)/LiF(0.8nm)/Ni(5nm)/Al
4. ITO/NPB(40nm)/Alq(80nm)/LiF( 2 nm)/Ni(5nm)/Al
Altering the region of doped Au can affect the MF effect, but there is a little difference between our experiment result and the expectation because the No.3 device is abnormal.
LiF layer can also improve the efficiency of the device based on the Ni cathode, but 0.8-1nm is not the best thickness. And when the LiF layer is thicker, the MF effect is stronger.
Summaries:
1. The strong spin-orbital coupling induced by mixing heavy metal element Au can reduce the Magnetic field
effect (MFE) on OLED.
2. As the current is reduced, the MFE becomes more obvious.
3. The existence of gold atoms reduces the magnetic effect on EL of OLED, and altering the region of doped Au
can affect the MFE.
4. Inserting LiF layer with different thickness can influence the MFE. When the LiF layer is thicker, the MF effect
is stronger.